Piezoelectric crystal holder



R. BECHMANN ET AL PIEZOELECTRIC CRYSTAL HOLDER Filed Aug, 4, 19

RUD

VENTORS BECHMANN HNEDER VAT ORNEY Patented May 11, 1937 UNITED STATESPATENT OFFICE PIEZOELECTRIC CRYSTAL HOLDER Rudolf Bechmann and WilhelmSchneider, Berlin, Germany, assignors to Telefunken Gesellschaft fiirDrahtlose Telegraphic m. b. H., Berlin, Germany, a. corporation ofGermany Application August 4, 1934, Serial No. 738,454 In Germany August29, 1933 Referring now to Fig. l. The piezo-electric quartz crystal Ibears on the electrode 2, the spacer ring 3 made of ceramic material,governs and maintains the distance of the electrode 4 which is fastenedin the cover plate 5. Where special forms of construction designed toinsure particularly great frequency stability are concerned it isadvantageous to have the crystal oscillation plate perfectly free anduntouched by the electrode. An embodiment of this kind is illustrated inFig. 2. In the central ring H the piezo-electric crystal oscillatorplate i2 is supported in its median plane by centering peaks or slots.The said centering ring is clamped fast on both sides by parts ofceramic material [3, !3a, by means of the screws 6 (Fig. 3) Theelectrodes l4 and. Ma which are shiftable in relation to the surface ofthe oscillable plate are adjustable inside the bushes I5 and 15cc havinga tapered shoulder which are embedded by means of a suitable binder inthe ceramic material and furnished with a fine-pitch screw-thread. Theadvantages of this holder device reside in a very low temperaturecoeflicient, very great mechanical stability, and very lowinter-electrode capacity. Another merit of this holder is that the same,contrasted with earlier holders, is of very low weight. A holder of thiskind is particularly valuable when used with piezo-electric oscillatorswith a very low temperature coefficient.

We claim:

1. A piezo-electric crystal holder comprising an insulating enclosingchamber formed in two parts and joined together at substantially thecenter, two metallic threaded bushings secured to the ends of saidenclosing chamber, a piezoelectric crystal secured within said chamber,adjustable electrodes located each side of said crystal, said adjustableelectrodes having a threaded stud cooperating with said threadedbushings to change the spacing between the crystal and said electrodes.

2. A piezo-electric crystal holder comprising an insulating enclosingchamber formed in two parts and joined together at substantially thecenter, two threaded tapered bushings embedded in the ends of saidenclosing chamber, a piezoelectric crystal secured within said chamber,adjustable electrodes located. each side of said crystal, saidadjustable electrodes having a threaded stud cooperating with saidthreaded tapered bushings to change the spacing between the crystal andsaid electrodes.

3. A piezo-electric crystal holder comprising an insulating enclosingchamber having substan- 6 Claims.

This invention relates to an improved method in the construction of thesetting or holder for piezo-electric crystals.

An object of the invention is to simplify and improve piezo-electriccrystal holders.

In the production of oscillations of stable frequency by means ofpiezo-electric crystal plates, the means of holding the oscillableplates plays an important part. What is essential in the supportingmeans for the crystal is that the position of the oscillable platesshould be absolutely fixed; moreover, that additional damping which willalways arise if the supporting means engages at points partaking of theoscillations, should be avoided. It is known in the prior art to supportfor this purpose the plates in the median zone by means of peaks orslots. It is also advantageous to so dispose the electrodes that theywill not touch the surface of the oscillating plates. However, in thepractical embodiments of these schemes as known in the prior artdifliculties arise which reside in that, with the use of metallicholding means the inter-electrode capacity becomes high. Another fact isthat in the known arrangements the influence of thermal expansion ismostly not negligible. As a result of the thermal expansion of the partsgoverning the distance between the electrodes and the oscillatorycrystal there occurs a change in this distance which results in a changeof the electrical natural period of the oscillatory system.

In what follows a novel support for the oscillatory crystal is disclosedwhich is the object of the present invention. As the material whichserves as the support of the electrodes there is used a ceramicmaterial, say, porcelain or other ceramic product known in technologyunder various names such as steatite, frequentite, calan, calite,sinterkorond, etc., which contain a mixture of soapstone and kaolin ormagnesium silicates free from iron. Suitable ceramic materials have avery low temperature coefiicient and small dielectric losses, but, onthe other hand, a very high insulation strength combined with highmechanical strength, all of which properties that are essential for ahigh-grade and efficient holder for piezo-electric oscillators.

This invention will be more clearly understood by referring to theaccompanying drawing, in which,

Fig. 1 is a sectional view of a simple crystal holder or support;

Fig. 2 is a sectional view of another form of crystal holder or support;

Fig. 3 is a plan view of Fig. 2.

tially zero temperature coefficient, said enclosing chamber beingseparated in two parts and joined together at substantially the center,a tapered aperture at each end of each part of said chamber, twometallic threaded bushings embedded in said enclosing chamber, apiezo-electric crystal secured within said chamber, adjustableelectrodes located each side of said crystal, said adjustable electrodeshaving a threaded stud cooperating with said threaded bushings to changethe spacing between the crystal and said electrodes. I

4. A piezo-electric crystal holder comprising an enclosing chamberformed of complementary sections, a threaded bushing located at one endof each complementary section, securing means for binding saidcomplementary sections together, a piezo-electric crystal secured withinsaid chamber, said crystal supported at its periphery by a ring-likemember clamped between said complementary sections, adjustableelectrodes located each side of said crystal, said adjustable electrodeshaving a threaded stud cooperating with said threaded bushings to changethe spacing between the crystal and said electrodes.

5. A piezo-electric crystal holder comprising an enclosing chamberformed of complementary sections, a threaded bushing located at one endof each complementary section, securing means for binding saidcomplementary sections to gether, a piezo-electric crystal supported bya ring like member, said ring like member being secured by saidcomplementary sections, adjustable electrodes located each side of saidcrystal, said adjustable electrodes having a threaded stud cooperatingwith said threaded bushings to change the spacing between the crystaland said electrodes.

6. A piezo-electric crystal holder comprising an enclosing chamberformed of complementary sections, a threaded bushing located at one endof each complementary section, securing means for binding saidcomplementary sections together, a piezo-electric crystal secured withinsaid chamber, said crystal having an annular groove, a ring-like memberhaving centering peaks to secure said crystal, said ring-like memberbeing clamped by said complementary sections, adjustable electrodeslocated each side of said crystal, said adjustable electrodes having athreaded stud cooperating with said threaded bushings to change thespacing between the crystal and said electrodes, each one of saidcomplementary sections and said electrodes being symmetrically arrangedwith respect to each other.

RUDOLF BECHMANN. WILHELM SCHNEIDER.

